Various thermoplastic resins have been used in a broad range of fields in recent years. Thermoplastic resins are superior in solubility in solvents and heat seal property, but inferior in heat resistance. For an improved heat resistance, a two-part adhesive comprising a thermoplastic resin and a curing agent has been used. However, a two-part adhesive has a limited working life (pot life). To provide an adhesive resin composition having relatively long pot life and capable of thermosetting, an epoxy resin as a main component and other ingredients are used in various combinations. For example, such combinations are used as an adhesive for circuit board. The adhesive for this use is required to have not only adhesive property but also superior heat resistance, chemical resistance, flexibility, electric insulating property and the like. Heretofore, poly(vinyl butyral) resin-epoxy resin type adhesive compositions, acrylonitrile-butadiene rubber-epoxy resin type adhesive compositions and adhesive compositions comprising phenol resin or acrylic rubber as a main component have been widely used. However, poly(vinyl butyral) resin-epoxy resin type adhesive compositions are inferior in the most desired adhesive property and other adhesive compositions mentioned above are inferior in heat resistance.
In case of a copper clad laminate for print circuit, the portion of the copper foil to form a conductive part that is other than the circuit part is chemically etched to give a wire board and the circuit board is perforated so that terminals for connection to electric parts can be formed. During this process, it is required that the board be free of blister when it is immersed in a molten solder bath (chemical resistance), and an adhesive film be free of peeling off when the chemical used for soldering is washed away with water (water resistance).
The adhesive composition for the above-mentioned use is required to have relatively long working life and superior properties of heat resistance, chemical resistance, flexibility, electrical insulating property and the like, besides adhesive property. Conventional adhesive compositions for use heretofore that contain a thermoplastic resin have insufficient heat resistance, and those containing a thermosetting resin have insufficient flexibility and shorter working life (pot life).